Prior art apparatus used primarily for the therapeutic stretching of the calf muscles of the lower leg are not usually linked with foot control. In order to properly stretch the calf muscles, it is necessary to position the foot in such a way as to increase the stability of the ligaments and joints of the foot while maintaining mobility of the ankle. The subtalar joint of the foot can be moved around one axis while the ankle joint is being moved around a different axis, if desired. It is also necessary for the motion in each plane to be controlled in a manner which provides a means for repetition of the same movements. Such control further prevents over extension of the muscles or ligaments which could cause additional damage to someone who has a physical impairment in that area.
The prior art discloses various means for exercising the ankle and feet. For example, U.S. Pat. No. 4,739,986 to Kucharik et al, describes a spring loaded ball joint apparatus which uses the swivel action of the ball and spring to exercise the ankle.
Seel et al, in U.S. Pat. No. 4,653,748, describes an ankle platform that sits on a hemisphere with the platform moved through various axes limited only by contact by the platform with the floor.
Dewees U.S. Pat. No. 4,635,932, describes a flexible foot plate for exercising the ankle through various planes of movement for the purpose of proprioceptive rehabilitation.
Troxel, in U.S. Pat. No. 4,605,220, describes an apparatus for exercising the muscles involved in dorsiflexion, plantarflexion, inversion, and eversion while preventing tibial rotation with some controlled limitations.
However, movement is limited to the four basic directions and in the longitudinal and transverse axis only. There is no control of the ankle and subtalar joint motion, and there is no provision for triplane rotation. Smith, in U.S. Pat. No. 4,951,938, discloses a semicircular exercise shoe in which the foot plate has heel and toe portions fixed at different angles and provides only dorsiflexion and plantartlexion exercise.
Kucharik and Troxel are mainly strengthening devices using spring and hydraulic resistance. However, Kucharik uses no control over the biplane movement, and Troxel provides control in only the longitudinal and transverse axis. Seel and Dewees do not provide for guided, controlled movement with respect to the subtalar joint. The Smith device does not provide biplane motion.
The above described apparatus fail to disclose a method for controlling the movement of muscles involved in dorsiflexion and plantarflexion in combination with inversion an eversion while preventing tibial rotation. Muscles affecting the triplane combinations of movements in the transverse, sagittal and frontal planes are specific and in unison. Injury to them constitutes a significant impairment to the foot and ankle function.
Only Seel's patent teaches the loading off the ankle, such as when standing, during the exercise routine. However, Seel makes no provision for controlling repetitive routines nor for the need to locate and position the subtalar joint based on each individual's need. Ankle exercise devices which are capable of rotating the ankle on an involuntary base such as that disclosed by Kost in U.S. Pat. No. 2,206,902 are slow, complicated and fail to properly load the ankle joint as is the case with other ankle exercise apparatus which require the user to be seated as disclosed in U.S. Pat. Nos. 4,501,421 and 478,166. Another type of ankle exercise apparatus are those which are not therapeutic in nature such as that used by a physical therapist or the like but used by individuals to strengthening the ankle and/or muscles. Such devices are disclosed by U.S. Pat. Nos. 5,135,450, 4,905,994 and French Patent 2,654,639. Although the U.S. Pat. No. 5,135,450 and the 2,654,639 patents do provide a rocking means they have very definite disadvantages. For example the invention disclosed by the French Patent requires both a left and right apparatus and has only one rocker located outboard each foot while utilizing a peg inboard of the stop as a pivotal means, restricting pivotal rotation and oscillations by a single heel stop. This arrangement makes rocking movement very jerky and erratic and could result in injury if not performed with great care. The U.S. Pat. No. 5,135,450 patent remedies the rocker problem but fails to provide arch support, thereby strengthening leg muscles but placing excessive strain on the ankle joint itself This patent further relies on a an elongated stop apparatus which is pivotal and allowed to move between fore and aft oscillations of the rocker thus creating a more cumbersome, expensive and complicated apparatus.
The prior art does not teach the need for ankle exercise apparatus attached to elliptical rockers having a foot plate which may be rotated perpendicular to the rockers thereby allowing eversion and inversion to be combined with dorsiflexion and plantarflexion.
It is, therefore an object of the present invention to improve ankle exercise technology in a manner which addresses the need for a controlled therapeutic regimen which links the motions of the foot and ankle with regard to the subtalar joint complex with extension of the calf muscle groups.
It is also an object of the present invention to provide a subtalar joint and muscle exercise apparatus which is repeatable and controllable in all three planes.
A further object of the present invention is the provision of an ankle exerciser that is versatile and useful to both the healthy and physically impaired individual. Still a further object of the present invention is the provision of an ankle exerciser whereby each adjustment setting for each set of repetitions can be recorded.
A further object of the present invention is to provide the user with a means for safely standing on the apparatus with one foot while exercising the foot, ankle and leg while providing normal loading of the subtalar joint and the lower extremity thus, providing normal, functional motion of the subtalar joint in the triplane motion and the ankle in the normal, Biplane motion.